Question

2x +8y =20
-5x-20y=-50

Answer 1

ax + by =12; 2x + 8y = 60. ax + by = 12; 2x + 8y = 60

Answer 2

System of Equations.
You can either substitute or eliminate a variable.

Substitue:
2x +8y =20
÷2 ÷2 ÷2
x +4y =10
x = -4y +10 (plug this into the second equation)
-5(-4y +10) -20y = -50 (distribute)
20y -50 -20y = -50
-50 = -50
0 = 0